The incidence of epilepsy declines after the first few years of life but remains higher than in adults.²¹ Greater maturity of the brain is associated with an increasing frequency of the classic types of seizures, such as generalized tonic–clonic, absence, and simple or complex partial seizures, and with a decreased incidence of the seizure types characteristic of infancy, such as infantile spasms, atypical absences, and febrile convulsions. Although lesional epilepsies of various causes can begin in this age range, a remarkable feature of many of the epilepsies of late childhood and adolescence is their occurrence in a previously normal child without neurologic or neurodevelopmental defects. Even more remarkable is the fact that a significant proportion of the epilepsies of late childhood and preadolescence tend to be self-limited and disappear after a few years without any detectable sequelae, and several such epilepsy syndromes with variable degree of benignity are described in the following chapters.

Such benign or favorable courses reflect the nonlesional nature of many of the epilepsies of this age, which are mainly determined by genetic factors.^14,16,32 Familial grouping of cases is well recognized, but there is still considerable uncertainty regarding the modes of inheritance of various types and the identification and localization of the responsible genes. Several monogenic syndromes have been described, but in most epilepsies of childhood and adolescence, only a few loci or genes have been characterized, and multigenic determination is considered probable. Even clinically homogeneous syndromes such as juvenile myoclonic epilepsy are genetically heterogeneous, and the current trend is to think in terms of susceptibility genes rather than of direct causation. This applies, for instance, to juvenile myoclonic epilepsy²³ and even more clearly to the syndrome of generalized epilepsy with febrile seizures plus (GEFS+), for which at least three genes have been identified,¹⁷ and probably to other epilepsies.³²

Two major groups of nonlesional, probably genetically determined, epilepsies are recognized: (a) the idiopathic generalized and (b) the benign partial epilepsies. The first group includes epilepsies with primary generalized tonic–clonic convulsions and several forms of myoclonic and absence epilepsies. The most common types in childhood and adolescence are childhood absence epilepsy (Chapter 239) and juvenile myoclonic epilepsy (Chapter 244). Absence epilepsy appears to be a clinically heterogeneous syndrome, and several distinct syndromes of absence epilepsy exist, whose recognition is probably important for prognostic purposes.²⁷ Childhood absence epilepsy has an excellent outcome, whereas juvenile absence epilepsy³⁴ and absences associated with juvenile myoclonic epilepsy are likely to persist into adult life. The exact nosologic place of some rare syndromes, such as eyelid myoclonia with absences⁴ and absences with prominent perioral myoclonus between absence and myoclonic epilepsies, is not definitely determined. Juvenile myoclonic epilepsy is a common and well-defined syndrome in adolescents. The characteristic myoclonus on awakening easily goes unrecognized, and the diagnosis is often missed, so that the correct prognosis and treatment might not be given.^9,23 Juvenile myoclonic epilepsy, idiopathic grand mal epilepsies, and juvenile absence epilepsy may represent a spectrum of related syndromes (sometimes termed primary generalized epilepsies) with some types presenting only tonic–clonic seizures (awakening grand mal) and others with associated juvenile absences. It is not clear whether these different clinical presentations form different electroclinical and/or genetic entities or more likely belong to what is basically a single condition due to a common predisposition with specific factors determining the seizure expression, so that the group might be better termed primary generalized epilepsy.³⁰ Despite these different clinical aspects, the epilepsies in this group are benign in terms of neurodevelopment but tend to be persistent and not to remit for many years. They may even be lifelong, thus requiring continuous treatment.

The second group of partial idiopathic epilepsies has proved to be one of the most common types of epilepsy in older children. Benign rolandic epilepsy (Chapter 236), first described in the 1960s,²⁴ has been extensively studied.⁵ The charactristic nocturnal sensorimotor facial seizures of short duration occurring in healthy children has now become familiar to neurologists and is easily recognized, even though the paroxysmal electroencephalogram (EEG) abnormalities may be more variable than initially thought.³⁴ The virtually complete benign nature of the syndrome has been repeatedly confirmed, although exceptional cases of an identical clinical syndrome in association with focal opercular lesions are on record.³ However, recent studies have shown that disturbances of language and of other cognitive and behavioral functions may often be found, usually to a mild degree.^11,12 Long- term follow-up studies are necessary to assess the significance of these findings.